1. Field of the Invention
The present invention relates to a rotating electric machine used for a vehicle or the like, which is linked to an engine, and particularly relates to a cooling mechanism for radiating heat generated from the rotating electric machine.
2. Description of the Related Art
In a conventional rotating electric machine used for a vehicle, it has been suggested that a power assembly having switching elements, which supply electric current to a rotor having armature coils, and a control assembly having a control circuit, which controls the power assembly, are mounted on the rotating electric machines (for example, refer to Patent Document 1 and Patent Document 2).
In the rotating electric machine described in Patent Document 1, power modules composed of power semiconductor devices, insulating substrates, and heat sinks are mounted on a bracket (housing), and fins are formed on the heat sink. A fan is mounted on a rotor, and cooling wind is generated by rotating the rotor. The rotating electric machine is configured in such a way that a window for passing wind is formed on the bracket, and the cooling wind passed through the fins is exhausted from an aperture of the bracket via the window of the bracket.
Patent Document    [Patent Document 1]    Japanese Laid-Open Patent Publication No. 2004-312852 (Embodiment 2, FIG. 3 and FIG. 5)    [Patent Document 2]    Japanese Laid-Open Patent Publication No. 2010-268541 (Embodiment 3, FIG. 7)
In the rotating electric machine described in Patent Document 1, power modules are mounted overall an end surface of the bracket, and in order to effectively use the fins formed on the heat sink, it is required that the window of the bracket is formed near a rotary shaft provided at a center of the rotating electric machine. However, the bracket must hold the rotor and the stator, and a metal material is usually used for the bracket because of a structural factor. Therefore, because components without the window are covered, there is a problem in that a weight of the rotating electric machine is increased. Moreover, the bracket holds the stator as described above, so that a temperature of the bracket becomes high by a heat transfer from the stator. Therefore, when a wind passage is configured by using the bracket and the heat sink, a cooling efficiency of the heat sink, on which power modules are mounted, is deteriorated by radiant heat transmitted from the bracket to the cooling wind or radiant heat transmitted from the bracket to the heat sink.
On the other hand, in the rotating electric machine described in Patent Document 2, it is suggested that a power circuit having switching elements is mounted on a surface of the heat sink, and fins are provided on the other surface, and a stator coil and a relay plate for connecting a stator coil and the power circuit are provided at an opposite side of the fins of the heat sink, and moreover, a wind passage is configured by using the heat sink and the relay plate.
In the rotating electric machine described in Patent Document 2, the heat sink, on which a power circuit is mounted, is mounted in the inside of the housing, so that there has been a problem in that an inlet for cooling wind is positioned near an outlet, and the exhausted air is circulated, whereby temperature of the aspirated air is increased. Moreover, it is required that a bus bar for connecting a stator coil to the power circuit is provided on the relay plate. Because the whole parts of the bus bar, without a connecting portion, must be insulated, a thickness of the relay plate is increased. When the thickness of the relay plate is increased, a size in an axis direction of the rotating electric machine is increased. Moreover, in order to prevent the size in an axis direction of the rotating electric machine from changing, it is required that the fins of the heat sink become short so as reduce the thickness of the relay plate. In a former case, the size of the rotating electric machine is increased, whereby the weight of the rotating electric machine is increased. In a later case, the fins become short, whereby a cooling capacity of the heat sink is deteriorated.